Molecular epidemiology, based on plasmid profiles, of Haemophilus ducreyi infections in the United States. Results of surveillance, 1981-1990.

To determine the distribution and extent of temporal changes in Haemophilus ducreyi strains in the United States, 342 isolates of H. ducreyi collected in 18 urban areas in the United States between 1981 and 1990 were characterized by plasmid content. Isolates possessed either no plasmid (29.8%), the 5.7-Mdal plasmid (50.9%), both the 4.4- and 5.7-Mdal plasmids (6.1%), the 3.2-Mdal plasmid (12.9%), or a combination of 1.8-, 2.6-, 2.8-, and 3.2-Mdal plasmids (1 case out of 342). Isolates that possessed no plasmid or that possessed the 5.7-Mdal plasmid had the widest geographic distribution; only isolates from cities on the West Coast possessed the 3.2-Mdal plasmid. Evidence was found of temporal changes in H. ducreyi strain populations among isolates from both Tampa and New Orleans.